In recent years, in semiconductor devices for controlling the power of hybrid vehicles and electric vehicles, and CPUs for high-speed computers, it has been desired to increase the thermal conductivity of a packaging material in order to prevent a temperature of an internal semiconductor from being too high. That is, an ability to effectively discharge heat generated from a semiconductor chip to the outside is important. In addition, due to a rise in the operation temperature, thermal distortion may occur due to a difference between thermal expansion coefficients of materials used in a package, and there is also a problem of a reduced lifespan due to peeling off of a wiring or the like.
As a method of solving such a heat dissipation problem, there is a method in which a highly heat conductive material (heat-dissipating member) is brought into contact with a heat generating part and heat is conducted to the outside, and heat dissipation is performed. Examples of a highly heat conductive material include inorganic materials such as a metal and a metal oxide. In particular, aluminum nitride is preferably used because it has a thermal expansion coefficient close to that of silicon. However, such inorganic materials have problems in terms of processability and being easily cracked, and it cannot be said that they have characteristics sufficient for a substrate material in a package. Therefore, development of a heat-dissipating member having high thermal conductivity by combining such inorganic materials and resins is underway.
In order to increase the thermal conductivity of a resin composite material, generally, a large amount of a metal filling material or an inorganic filling material is added to a general purpose resin such as a silicone resin, a polyamide resin, a polystyrene resin, an acrylic resin, and an epoxy resin. However, the thermal conductivity of an inorganic filling material has a value unique to that substance and has an upper limit that is fixed. Therefore, many methods of improving the thermal conductivity of a resin and increasing the thermal conductivity of a composite material are being attempted.
In Patent Literature 1, as a method of improving the thermal conductivity of a resin, a heat-dissipating member obtained by performing alignment control and polymerization of a liquid crystal composition using an alignment control additive or rubbing treatment method is disclosed.